1. Field of the Invention
The present invention relates generally to an image forming apparatus. More particularly, the present invention relates to an image forming apparatus, such as an electrophotographic copying machine, a laser printer, etc. in which an electrostatic latent image formed on a photoreceptor is toner-developed by using a dual-component developer consisting of carrier particles and toner particles.
2. Description of the Prior Art
As described in, for example, U.S. Pat. No. 5,012,286 and U.S. Pat No. 4,956,668, in this type of image forming apparatus, constant amounts of toner particles are supplied only when a toner concentration sensor senses that a toner concentration is not more than a predetermined value. Consequently, the toner concentration temporarily varies until such value is sensed. In the conventional image forming apparatus, therefore, there occurs a decrease in image quality due to the variation in the toner concentration.